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This invention relates to improvements in spontaneously formed clear microemulsions generally described in U.S. Pat. No. 5,705,562 (Jan. 6, 1998), which is assigned to the same assignee as this invention.
The focus of U.S. Pat. No. 5,705,562 is on (i) oil-in-water (O/W) microemulsions, and (ii) silicone polyether surfactants which are water soluble; whereas the focus of the present invention is on (i) water-in-oil (W/O) microemulsions, and (ii) silicone polyether surfactants which are oil soluble, with the intention of preparing distinctly W/O microemulsions containing only relatively small amounts of water.
In particular, a side-by-side comparison between this invention and U.S. Pat. No. 5,705,562 is shown in Table 1. In Table 1, the parameters a-c, m, n, and x-z, represent integers in the structure of silicone polyether surfactants shown more fully hereinafter.
What has been unexpectedly discovered herein is that when b is limited to the range of 2 to 6, rather than 4 to 20 as in U.S. Pat. No. 5,705,562, the silicone polyether surfactants are only oil soluble and form distinctly water-in-oil microemulsions containing only 0.1 to 9 percent by weight of water. This is a greater than two-fold reduction, compared to the microemulsions containing 20 to 60 percent by weight of water in U.S. Pat. No. 5,705,562.
In addition, it is possible to prepare distinctly water-in-oil microemulsions containing greater than 80 percent by weight of an oil component, compared to microemulsions in U.S. Pat. No. 5,705,562 which contain 40 to 80 percent by weight oil. A third distinction according to this invention is that much less silicone polyether surfactant is needed, i.e., 3 to 10 percent by weight, compared to 5-70 percent by weight in U.S. Pat. No. 5,705,562.
The invention is directed to a microemulsion containing (i) 0.1 to 9 percent by weight of water; (ii) greater than 80 percent by weight of a cyclic alkyl siloxane of the formula (R2SiO)p or a linear alkyl siloxane of the formula R3SiO(R2SiO)qSiR3 in which R is an alkyl group containing 1-6 carbon atoms, p is 3-6, and q is 0-5; and (iii) 3 to 10 percent by weight of silicone polyether having an average structure represented by one of the following: 
where R1 is an alkyl group containing 1-6 carbon atoms; R2 represents the radical xe2x80x94(CH2)aO(aO(C2H4O)b(C3H6O)CR3; x has a value of 0-3; y has a value of 1-3; z has a value of 0-2; m has a value of 3-5; n is one; a has a value of 0-6; b has a value of 2-6; c has a value of 0-3; and R3 is hydrogen, a methyl radical, or an acyl radical.
Preferably, the alkyl siloxane is a cyclic methyl siloxane of the formula {(CH3)2SiO}p or linear methyl siloxane of the formula (CH3)3SiO{(CH3)2SiO}qSi(CH3)3 in which p is 3-6 and q is 0-5, respectively.
By greater than 80 percent by weight is meant that the microemulsion should contain 81 to 96.9 percent by weight of the alkyl siloxane. Most preferred, are microemulsions containing greater than 85 percent by weight of alkyl siloxane.
The invention is also directed to personal care products containing these microemulsions, and to methods of treating hair or skin by applying to hair or skin compositions containing these microemulsions.
These and other features of the invention will become apparent from a consideration of the detailed description.